The Musculus splenius capitis of hummingbirds <i>Trochilidae</i>

The peculiar crossover origin of the cervical Musculus splenius capitis was studied in 32 hummingbird species. In this avian family the cruciform neck muscle exhibits extreme intra‐ and interspecific variations independent of age, thus taxa clustering for phylogenetical purposes according to the muscle's distinctive features is impossible. It is argued that the Musculus splenius capitis serves primarily to control precisely fast sideward head movements of hummingbirds while they are preying on insects.